28mm Lens with Letus Econ. issue!

jgastelb

jgastelb

Well-known member
Hi,
I'm having some problems with my new 28mm Canon FD lens -- f2.8. It seems to create a very hot spot in the center or a extremely dark vignette around the edges. I have another two lenses --50mm and 200mm and they both work great so I'm not sure what the problem is. It obviously has to be the new lens. I was wondering if anyone had any ideas or has experienced the same thing. I talked to one of the guys from the Letus company and he doesn't know what it could be either. I'm puzzled here. When I look at the 28mm lens without the adapter I can't see any problems. Any tips would be greatly appreciated! Thanks!

Here's the effect --

Zoomed way out...
Image0.jpg



Zoomed in...
Image1.jpg
 
You've got two issues there. One is that the alignment is about 20% skewed to the right, and the other is the edge falloff. Edge falloff is an issue that is hard to deal with on wide angle lenses..but you should definitely consult the Letus guys on this one.
 
Why am I seeing a black area above and below the kitchen? That looks to me like the top and bottom of the GG...if that is the case, you need to be zoomed in way past this.
 
Dennis Wood said:
You've got two issues there. One is that the alignment is about 20% skewed to the right, and the other is the edge falloff. Edge falloff is an issue that is hard to deal with on wide angle lenses..but you should definitely consult the Letus guys on this one.
Click to expand...

I talked to the Letus guys and they didn't know.
I noticed the misalignment as well but with the other lenses as long as I get to Zoom 85 or beyond with the DVX100B then it works perfectly.
 
I am going to suggest you do a test and post a still. Point your camera at a strong light source, like the sky. Don't include anything else in the frame. Capture the footage and post a still. I want to see clearly that you have zoomed in all the way.

What camera are you using?
 
disjecta said:
I am going to suggest you do a test and post a still. Point your camera at a strong light source, like the sky. Don't include anything else in the frame. Capture the footage and post a still. I want to see clearly that you have zoomed in all the way.

What camera are you using?
Click to expand...

Here you go, bud. Three grabs.

Zoomed in at Z73 --

Z73.jpg


at Z79 --
Z79.jpg


Z94 way past the frame here. At this point it means that my 28mm looks like almost the same distance as if I used the 50mm lens that lets me stay comfortably at Z85. This defeats the purpose of a wide lens in my book. Hope this clarifies the situation --

Z94withtext.jpg
 
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jgastelb said:
At this point it means that my 28mm looks like almost the same distance as if I used the 50mm lens that lets me stay comfortably at Z85. This defeats the purpose of a wide lens in my book. Hope this clarifies the situation --
Click to expand...

28mm Z99 (vignette still shows)

Z99_28mm.jpg


50mm Z85 (SAME DISTANCE & ANGLE)...
Z85_50mm.jpg
 
This is weird....I'm using the letus economy as well, but I only need to zoom in to Z75 with a 50mm lens to eliminate vignetting. In fact, Z70 is fine for me, but i zoom in to Z75 as a precaution to ensure i don't get vignetting. I'm shooting on a DVX102b PAL. Does the 28mm lens work fine when you use it on a still camera?

Shot with a 50mm f1.8 at Z75
28991664av1.jpg
 
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Oedipax said:
Does the vignette change if you stop down the lens?
Click to expand...

It gets darker. It looks as if someone was slightly covering part of the lens with their hands, feathered into the frame. Yet I don't see it with just the lens itself.
 
MalcolmOng said:
This is weird....I'm using the letus economy as well, but I only need to zoom in to Z75 with a 50mm lens to eliminate vignetting. In fact, Z70 is fine for me, but i zoom in to Z75 as a precaution to ensure i don't get vignetting. I'm shooting on a DVX102b PAL. Does the 28mm lens work fine when you use it on a still camera?

Shot with a 50mm f1.8 at Z75
Click to expand...

I think I may have to align my letus for it to work like yours. It's just that if I do I may have to change where the battery compartment goes which already has the velcro attached. But, yeah. I would love to be able to not have to zoom in so much. Thanks for the tip. The frame is slightly to the right right now.
Jgastelb
 
Most likely your FD mount lens apeture is stuck. Can you show a picture of the lens apeture? Have you tried changing the apeture ring and seeing if it opens up or close down ? I had the same problem with my old FD lenses. B ut I just push the level up and in stay in place instead of some of the guys here using a toothpick to make it stay in place.
 
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I went ahead and purchased another lens thinking that the first one may have some defect. However, this new lens also shows the same strong vignette where you have to be zoomed in pretty much all the way in the get rid of it. I have contacted the Letus people to see what the deal is here.

Has anyone here had success with the Economy and wide angle lenses? I know that most people are with the Extreme but there has to be someone else other than me with an Economy.

Jgastelb
 
DavidChia said:
Most likely your FD mount lens apeture is stuck. Can you show a picture of the lens apeture? Have you tried changing the apeture ring and seeing if it opens up or close down ? I had the same problem with my old FD lenses. B ut I just push the level up and in stay in place instead of some of the guys here using a toothpick to make it stay in place.
Click to expand...

I changed the aperture in the new lense with a paper clip stuck inside. Good old trick but to no avail. The issue remains. The original lens I purchased was wide open when I took the previous grabs you have seen in this thread. Thanks for trying to help though.
 
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